|Identification and Analysis of Atmospheric particles
We use a range of electron-beam instruments, prominent among which are our unsurpassed transmission electron microscopes (TEMs) for the chemical and structural analysis of individual aerosol particles. Together, they provide unsurpassed facilities for studying the chemistry and structures of fine-grained aerosol materials, their origin, and how they react to form other compounds.
The main analytical techniques that we use to characterize aerosol particles are X-ray emission spectroscopy by energy analysis (EDS), electron energy-loss spectroscopy (EELS), selected-area electron diffraction (SAED), and high-resolution imaging (HRTEM).
Of particular interest is determining the sources and sinks of pollutants in both the remote and urban environments. Emphasis is both on developing analytical procedures and on applying them to problems of environmental significance. Samples from diverse localities such as the Arctic, Indian Ocean, S. and equatorial Pacific, N. Atlantic, southern Africa, the Middle East, and Phoenix are being, or have been, studied.
We regularly participate in major international research programs designed to determine the character and role of particulate aerosols in the lower atmosphere. The large experiments involve integrated measurements from ships, airplanes, satellites, and ground stations, with participating researchers from universities and government laboratories across the U.S. and overseas. Our role is to analyze and compare inorganic aerosol particles collected in both the relatively pollution-free and polluted air masses.
As an example, the southern African continent commonly contains a stable air mass that accumulates large amounts of emissions from biomass burning as well as the major power plants (5 of the 10 world's largest) and industrial processes, many associated with mining. The result is pervasive air pollution at certain times of the year. We participated in a multi-institutional project to understand the sources and airborne reactions. This large international experiment is also being used by NASA to calibrate and test the results from its new TERRA and other Earth-orbiting satellites for remote monitoring of air quality from space. Our aerosol samples were collected from research airplanes that have sampled over various parts and altitudes over southern Africa. We stud these materials using transmission and scanning electron microscopy.
In addition to the international projects, together with colleagues in our College of Engineering, we have been involved in the local Phoenix Air Flow Experiments (PAFEX). The PAFEX experiments are unique in that, in addition to ground measurements, data was collected at various vertical levels with a tethered balloon. The PAFEX experiments took place during January 1998 near central Phoenix (PAFEX-I), and during July/August 1998 about 30 miles northeast of central Phoenix (PAFEX-II). The primary goal of both field projects was to gain a better understanding of the concentration and types of particulate pollutants, in addition to gaining insight into the urban meteorology and the dispersion of particulate and gaseous pollutants throughout the Phoenix metropolitan area. Individual and bulk analyses were used to count and characterize the particulate data using SEM and proton-induced X-ray emission (PIXE) measurements, respectively.
Support: NSF and UCAR
Links to selected other web sites:
International Global Atmospheric Chemistry (IGAC) Program
NASA Global Tropospheric Experiment
Phoenix Air Flow Experiment
US Department of Energy Atmospheric Chemistry Program (ACP)